A massive demonic invasion has overwhelmed the Union Aerospace Corporation's Mars Research Facility, leaving only chaos and horror in its wake. As one of only a few survivors, you must fight your way to hell and back against a horde of evil monsters.
IMPORTANT NOTE: This Patch is for CD-Retail version only, do not attempt to install it on BFG Edition or Steam version because those should already be updated.
Warning :This patch is for 2004 Edition game owners only, BFG Edition owners do not install this patch .
This patch is unlike 1.3.1 , it doesn't require any previous patch released in order to update your game to 1.3.1, it directly updates it to that version, in other word it contains all files needed to run the game without need to install any previous patch, here's why you should install this instead of the official patch :
This patch has been only tested with CD-Retail 2004 version of the game, so it will not work with BFG Edition, it should also work for every version of the game .
How to install the patch :
How to find out whether the patch worked or not : Start up the game and open the Console, It should tell you what game version are you running on bottom left of console .